Diamond and diamondlike platings and films have a number of properties resembling those of corresponding traditional diamonds. The first property is hardness. Another significant mechanical property is a low friction coefficient. The resistance to wear is also excellent. Moreover, such a plating or film remains unchanged in all known bases and acids. Thus, diamondlike platings and films are especially applicable for the coating of bodies subject to wear and corrosion, such as non-lubricated bearings. Another notable feature is the high refraction coefficient of diamonds.
WO publication 89/06708 presents an apparatus for diamond plating. The apparatus described in this publication works by forming from carbon by means of a plasma accelerator a plasma spray which is accelerated and deflected toward the body to be plated. The plasma accelerator has a cylindrical graphite cathode, A conducting rod serving as a firing device is placed inside the cathode.
During plating, carbon in the form of charged ions and uncharged atoms is released from the cathode. The surface of the cathode which releases carbon is subject to erosion, which may manifest itself, e.g., in the form of microscopic holes appearing in the cathode surface, producing spongy structures. At first, the arc is normally started from the cathode surface, but with the progress of erosion the starting of the arc occurs more and more frequently at the bottom of the holes. Gradually the holes are covered up and the cathode becomes incapable of emitting a plasma pulse.
For this reason, the cathode surface has to be smoothed out. This is generally accomplished by removing the cathode and refacing it, e.g., by turning. This is a complicated procedure, however. Moreover, it is impossible to keep the plating apparatus running continuously for a long time. Typically, the cathode has to be refaced every few hours.